The present invention generally relates to circuit boards and methods of producing circuit boards, and more particularly to a circuit board used in electronic devices and a method of producing such a circuit board.
Generally, a circuit board comprises an insulating substrate such as a ceramic substrate and a conductor layer formed on the ceramic substrate by use of the thick film technology. However, according to the thick film technology, the printed conductor layer on the ceramic substrate is baked at a high temperature of approximately 850.degree. C. When the circuit board is subjected to a process under such a high temperature, there is a problem in that cracks are easily formed in the conductor layer.
On the other hand, when there is a need to electrically connect two conductor layers formed on opposite sides of the ceramic substrate, it is necessary to provide a conductive pin which penetrates the ceramic substrate and solder both ends of the conductive pin to the respective conductor layers on the ceramic substrate. This is because, even when there is a through hole penetrating the ceramic substrate, the through hole will not be filled with the conductor when the conductor layers are formed on both sides of the ceramic substrate using the thick film technology. As a result, there is a problem in that troublesome processes of inserting the conductive pin into the through hole and soldering the ends of the conductive pin are required in order to electrically connect the two conductor layers on the opposite sides of the ceramic substrate. In other words, the number of parts required and the number processes required increase when such an electrical connection is needed.